Pen



FIG. 1 is a top plan view of a pen in accordance with the new design;

FIG. 2 is a right side elevational view thereof, a left side elevational view being a mirror image thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a front elevational view thereof; and,

FIG. 5 is a rear elevational view thereof.

The broken lines shown in FIGS. 1-4 illustrate portions of the pen that form no part of the claimed design. 

CLAIM The ornamental design for a pen, as shown and described. 